Various techniques have been recently developed for realizing magnetic disk devices having high storage capacity (such as HDDs). One of these techniques is a recording technique called shingled-write magnetic recording (SMR) or shingled-write recording (SWR). In a magnetic disk device of shingled-write magnetic recording, a track is written so that it overlaps an adjacent track written immediately before the first-mentioned track. The track density (tracks per inch [TPI]) can be improved by adopting shingled-write magnetic recording.
In the case of an HDD realizing standard recording, the distance (trackwidth) between adjacent tracks is determined from the width of a write head (write core). In the case of an HDD realizing shingled-write magnetic recording, the trackwidth does not depend upon the width of the write core, but upon an area where adjacent tracks overlap each other. Accordingly, in the HDD realizing shingled-write magnetic recording, it is important to control narrowing of the trackwidth due to the positioning error of the center of the head with respect to a target path.
Therefore, in the HDD realizing shingled-write magnetic recording, a trackwidth control function for suppressing narrowing of the trackwidth has been proposed. For example, a function (dynamic drift-off level [DDOL]) of inhibiting a data write operation when the offset exceeds a threshold determined from the positioning error of an adjacent track, or a function (automatic trackwidth control [ATC]) of setting the target path of a track based on positioning error data of an adjacent track to which data has been written, has been proposed. In the trackwidth control function, such as DDOL or ATC, when data is written, position data including a position error corresponding to one or two already written tracks is stored in a memory.
In a magnetic disk device realizing shingled-write magnetic recording, when the trackwidth control function, such as DDOL or ATC, is executed on respective multi-streams, it is difficult to manage position data items corresponding to a plurality of bands, using only a memory. Further, in the magnetic disk device realizing shingled-write magnetic recording, when data is newly added immediately after already written data, using the trackwidth control function, such as DDOL or ATC, it is difficult to manage position data items corresponding to a plurality of bands, using only a memory.